Much ado about something
 What is Vacuum, such as in Space, is there vacuum between the atoms of
water molecules? Is Vacuum a squishable-stretchable thing? oooo, this
fascinates me. Andre, Vancouver, Canada
A look at 'vacuum energy.' The animation shows the inside of a proton
where a quark and an anti-quark pop into existence, causing a hole in the
vacuum-field fluctuations. (Three quarks make up a proton. Protons and
electrons make up atoms; atoms make up molecules.)
The two spheres represent the quark and
anti-quark. The tube between them depicts the hole. Animation courtesy of
Derek B. Leinweber, CSSM,
University of Adelaide, copyright, used with permission.
A perfect vacuum. Ah, for the good old days of Aristotle and Newton, when we simply thought of a
perfect vacuum as a volume of completely empty space, containing nothing. Such a volume
would have zero pressure.
Nonsense, Plato said. There can never be nothing.
Now we know Plato was right, but for reasons that don't make intuitive sense.
Consider an electron. It's both a particle and a wave. Since it has
wave-like properties, its position is smeared out. According to the Heisenberg Uncertainty Principle, we can never know both the electron's
exact position and momentum at the same time. But that means any small
volume of space could have particles within it, which means no volume of
space can ever be a perfect vacuum, for certain.
There's also another effect involving gluons (which are tiny massless
particles that 'glue' quarks together inside a proton), says physicist
Derek B. Leinweber,
professor at University of Adelaide in Australia. Suppose we had an empty vacuum.
It won't stay empty long, because if we drop a single gluon into it — the vacuum
becomes unstable. It changes! The single gluon triggers the creation
of a "sea" of interacting quarks and gluons — in the vacuum. The
sea seethes with energy, and releases that energy in huge quantities.
So, to answer your question, no perfect vacuum exists between the atoms of
water molecules.
Experimental evidence. Moreover, not just theory, but also experimental evidence
(the Casimir effect) suggests vacuum is not empty. Put two metallic plates close together —
about a tenth of a micron (the length of the smallest bacteria on Earth).
Vacuum energy causes a measurable attractive force between them. "In fact,
this force can be the dominant force in the micro world," physicist
Erik Ramberg of Fermilab emails. "It is related to the Van der
Waals forces that exist between millions of individual water molecules.
Even the stickiness of a gecko's foot can be fundamentally related to these tiny
vacuum forces. Crazy!"
The Casimir effect is similar to the pull between tall sailing ships.
Long ago, when two schooners sailed side-by-side and sufficiently close together
in rough seas, they pulled together and actually crashed. Sailors had no
idea why. We now know it's because only certain length ocean waves can fit
in the space between the two close-together ships. But all-length waves
travel the open ocean. The inside waves tend to push out just as the
outside waves tend to push in. The few waves inside don't have a chance in
this shoving match. The huge numbers outside overcome the inside ones, and
push the ships together.
Similarly, the photons that pop into and out of existence in a vacuum have
wave-like properties, and exhibit all wavelengths. But only certain
wavelengths fit between the two plates. So the outside waves overcome the
inside ones, and push the plates towards each other a measurable amount.
The density of space vacuum. The vacuum of space between stars is about hundred trillion times less dense
than .the vacuum in a thermos bottle. A cubic centimeter of interstellar
space —
about the volume of a standard shooting marble — holds, on the average, a
single hydrogen atom. That's it, usually. That marble-sized volume
could also hold cosmic dust, but dust is found about 1000 times less often.
A squishable-stretchable thing? Your question about vacuum being a squishable-stretchable thing is, indeed,
fascinating stuff, which physicists fight about and outrages our intuition.
As mentioned above, we live in a universe of particles and
anti-particles that constantly wink into and out of existence in pairs so quickly they
can violate a strict relationship between the particle's energy and momentum, and get away with it. The
particles borrow energy from the vacuum to pop into existence, and pay it back
by annihilating each other in a flash of energy. So, the vacuum energy
constantly changes — bigger sometimes, and smaller other times.
The change can be enormous, and may account for the origin of our Universe.
The sea of particles, thus, roils
with energy, which is present even at absolute zero (-273 degrees Celsius) and
when no stable matter is present. We call this energy 'vacuum energy' and
'zero-point energy.'
Vacuum energy's origin. Where vacuum energy came from originally is debatable. One group thinks
it's left over energy from the big bang. Another says it came from
randomly foaming energy existing before the big bang and, indeed, is the
giant fluctuation that produced our universe.
Physicists also disagree about the amount of energy in empty-space vacuum.
Harold E. Puthoff, a quantum physicist at the
Institute for Advanced Studies at Austin, Texas states there's enough such
energy in a coffee-cup sized space to evaporate all Earth's oceans. Cosmic
physicist Steven Weinberg of the University of Texas, a Nobel-prize winner, says the amount of energy in an Earth-sized space
probably is equivalent to a gallon of gasoline.
Why the tremendous disparity? We have no theory that predicts gravity effects on fundamental particles.
The theories we do have — quantum mechanics for small-scale particle
interaction and gravity for large-scale object interaction — are not
appropriate for gravity effects on particles, and thus disagree wildly. A
new physics involving perhaps extra dimensions may eventually do the job,
accurately. But we're not there yet.
Back to your question, space vacuum is stretchable in the sense that its energy apparently has
changed from something close to Puthoff's value (huge) at the time of the big
bang to something close to Weinberg's value (tiny) now. How did it change?
We don't know, yet.
Further Reading:
Visualizations of quantum chromodynamics, Centre for the Subatomic Structure
of Matter and Department of Physics, University of Adelaide, Australia
The five ages of the Universe, Fred C. Adams, Greg Laughlin, 1999.
New energy age, Ask the experts, Scientific American frontiers archives, PBS
The
quantum designer, Harvard Magazine, Jan-Feb 2005
Zero-point energy,
Calphysics Institute
Bacteria,
Sizes.com
What is the 'zero-point energy' (or 'vacuum energy') in quantum physics?,
Scientific American, Aug. 18, 1997
Van der Waal forces, PhysLink.com
Density of outer space, The Physics Fact Book
Vacuum,
Wikipedia
Readers' Comments:
- I was pleasantly surprised to see Hal Puthoff's name in the article on vacuum.
He and I were participants in a summer think tank at Princeton back in the mid
90s on setting a research agenda for studying consciousness -- human, animal,
artificial, and maybe even alien varieties. It certainly changed my ontological
perspective on the existence of the world.
Why I comment on this is that I think it is essentially futile to give
mechanistic descriptions or visualizations of QM-level phenomena; it only delays
the Aha! experience of existentially coming to grips with a universe that's not
what it seems. (I am a firm believer that the wavelike characteristics of matter
are the more fundamental, and that extensibility of properties of matter into
geometric space arose from the Cosmic Whim's need to keep everything from
happening at once.) Bob, Marietta, Georgia
- I feel that until such time as we all are fully aware of, and appreciate
the immutable characteristics of the Aether, as being the sole source of all
the Energies revealed in the Universe, then many of the theories regarding the
physics of the Universe, (including the Casimir effect, are pointless. The
source of our energies is beyond our
abilities to ever replicate this phenomena, we will never discover any
particles of anything from the structure of the Aether,however we (Universe)
will always be able to extract these energies as we need them.
Brian, Perth, Western Australia
New Comment --- add your comments to the
discussion:
(Answered Dec. 10, 2007)
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